The World’s Smallest Compasses

An Amazing Discovery of How Humble Bacteria Can Sense Direction

The gifts and talents conferred on each creature, even the tiniest, fit their role in nature and their ecological requirements.

There is nothing, many outdoor enthusiasts
agree, like the odours from mud at the bottom of ponds and marshes. To sniff these
characteristic scents is to think of happy adventures like the time the canoe
got stuck in the marsh. The mud, with its bad smell and consistency like glue,
is merely incidental to the happy occasion. Most of us would rather not disturb
these sediments, nor release the contained gases.

Some people,
however, make careers out of studying organisms in smelly marsh mud. Richard P.
Blakemore was such an individual. As a graduate student at the University of Massachusetts,
his job in the summer of 1975 was to collect bacteria from the mud of brackish
marshes along the Atlantic coast. After each expedition, having collected odoriferous
samples of mud, he would return to the laboratory to grow cultures of the organisms
in his samples.

One strain of bacteria reacted in a most unexpected
way. No matter what the environmental conditions, these organisms persisted in
swimming northward in the water so that they always accumulated at the northern
edge of the droplet on the microscope slide. Mr Blakemore wondered if these organisms
(about two-thousandths of a millimetre long and about a quarter as wide) were
sensing magnetic north.

There is evidence that not only a wide variety of bacteria, but also some algae, insects, slugs and pigeons may use sophisticated magnetic compasses.

A bar magnet was placed on the microscope,
thereby overriding the earth’s magnetic field. The bacteria did indeed change
direction, swimming to the north end of the magnet. With this simple study, Mr
Blakemore opened the door to a new field in biology: navigation of organisms by
magnetic cues.1 There is
evidence that not only a wide variety of bacteria, but also some algae, insects,
slugs and pigeons may use sophisticated magnetic compasses.

Evolutionists
generally do not like the idea that living creatures illustrate good ‘design’—because
design suggests God, the omniscient Creator. They prefer to believe that organisms
came about on their own, through processes which had no intelligent direction.
They generally say organisms are ‘adapted’ rather than designed. Nevertheless,
famous evolutionist Stephen Jay Gould proclaimed the new magnetic bacterium to
be a ‘striking example of good design: an organism that builds an exquisite
machine within its own body. The machine is a magnet; the organism a “lowly”
bacterium.’2

Cultures
from more than a dozen types of bacteria have, since 1975, been found to display
magnetic responses. Muds from both freshwater and marine environments, as well
as sewage treatment ponds, have included such talented microorganisms.

What
amazing machines magnetic bacteria have been shown to contain. The magnet in these
tiny cells is made up of 20 or so roughly cubic particles arranged in a line along
the long axis of the cell. Each particle is about 50 nm (nanometres) on each side
(a nm is 10-9 m or one millionth of a millimetre). These particles
are not only the appropriate size for their host cells, but in physical terms
they represent the only design that would work as a magnet on this small scale.

The
particles are made of a type of iron oxide called magnetite or lodestone. In the
laboratory it is difficult to make magnetite particles of this small size. Biologists
are unsure how the bacteria achieve such precision.

Anyone
who has looked through the microscope at tiny objects suspended in water cannot
fail to notice how they are all in constant vibrating motion, even in living cells.
This ‘Brownian’ motion results from random jostling of molecules,
and the warmer they are, the faster they move.

The magnetite
particles, however, must not be jostled by Brownian motion, otherwise there would
be no magnetic orientation. Thus each particle must be able to orient itself firmly
in the direction of the earth’s magnetic field.

Other
than as interesting curiosities, what benefit could bacteria receive from the
ability to swim in a northerly direction? Biologists believe that this ability
may provide a mechanism to enable bacteria to orient themselves in space. Large
organisms know where they are relative to earth’s surface because gravity
provides the cue. This is much harder for bacteria, however, because of their
small size—gravity is very weak in comparison to other forces like surface
tension for example.

In the northern hemisphere, not only do
magnets point in the direction of the north magnetic pole (on a horizontal axis)
but the needle also dips down. The further north one is located, the steeper is
the incline of the magnet’s needle. At the north pole the needle points
straight down. In the southern hemisphere the needle points more steeply up, the
further one moves to the south.

Scientists suspect that magnets
in the northern hemisphere may indicate to these tiny cells which direction is
down. In the southern hemisphere such magnets would indicate the opposite direction—up. At the equator, however, magnets are no help.

These
bacteria are apparently using compasses to swim downward in the sediments. Most
of these organisms can tolerate little or no oxygen in their environment. Generally
there is a trend to lower oxygen levels as one moves down in the mud. The magnetic
cue enables these organisms to move down, away from higher oxygen concentrations.
This phenomenon represents an unusual and sophisticated solution to a common problem
for microorganisms.

This is one of those wonders in nature
which, only a few years ago, we could scarcely imagine.

The
gifts and talents conferred on each creature, even the tiniest, fit their role
in nature and their ecological requirements. How wonderful is their Creator!

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Answers in Genesis is an apologetics ministry, dedicated to helping Christians defend their faith and proclaim the gospel of Jesus Christ effectively. We focus on providing answers to questions about the Bible—particularly the book of Genesis—regarding key issues such as creation, evolution, science, and the age of the earth.